Étude du procédé de mise en forme par application de lignes de chauffe effectuées sur plaques d'acier inoxydable 304L

Abstract

Hot forming steel plates is a common manufacturing process in several industries, including Francis turbine blades. Due to the differences in the working conditions, turbine blades can be different from one site to another. Therefore, the geometry of the forming dies are unique to each set of turbine blades. The forming dies are usually made of high strength steel rising the cost of the process for small batches. In this thesis, thermal forming by line heating is presented as an alternative to the hot forming process. Line heating process consists of passing a heat source, such as a flame, over a steel plate in order to bend it. This forming methodology has proven to be efficient for ship hull builders. An experimental study was carried out with an oxyacetylene torch. The temperature through the thickness of the steel plate have been recorded during the passage of the flame. The deformation of the plate after it returns to room temperature was also measured. Then, the experiment was modeled using the finite element method (FEM) in Ansys software. Although the finite element (FE) results matched the experimental results with a small margin of error, the simulation time, even for a single heating line, was quite long. Forming gradually a plate by line heating to a targeted geometry requires significant number of passes, making the modeling the line heating sequence by FEM a cumbersome approach. As an alternative to the FEM, a differential geometry reconstruction algorithm is proposed. This algorithm uses the curvatures of a three-dimensional surface. By combining the fundamentals coefficients related to curvatures of each heating line and integrating the result of their sum, it is possible to estimate the final shape of the plate. The locations of the highest curvatures on the desired geometry point where the formed plate should be bent and consequently where the heating line would be efficiently applied. The developed algorithm allows to define the line heating trajectory and to estimate the number of passes required to obtain a certain shape by comparing the fundamental coefficients of the desired shape to the actual shape of the plate. This approach was applied to a simple pattern of heating lines and the difference in displacement between the FEM solution and the algorithm is about 6%. With this developed methodology, the results were obtained in a minute compared to hours required to solve the thermal-structural FE model.

Date	7 Nov 2017
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Henri Champliaud (Supervisor) & Javad Gholipour Baradari (Co-supervisor)